/*
 *   Copyright 2021 zzh
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 *
 */

package com.aduib.boot.common.util;

import java.net.InetAddress;

/** @Author 张代浩 */
public class UUIDGenerator {

  private static final int IP;
  private static final int JVM = (int) (System.currentTimeMillis() >>> 8);
  private static short counter = (short) 0;

  static {
    int ipadd;
    try {
      ipadd = toInt(InetAddress.getLocalHost().getAddress());
    } catch (Exception e) {
      ipadd = 0;
    }
    IP = ipadd;
  }

  /**
   * 产生一个32位的UUID
   *
   */
  public static String generate() {
    return format(getIP()) +
            format(getJVM()) +
            format(getHiTime()) +
            format(getLoTime()) +
            format(getCount());
  }

  private static String format(int intval) {
    String formatted = Integer.toHexString(intval);
    StringBuilder buf = new StringBuilder("00000000");
    buf.replace(8 - formatted.length(), 8, formatted);
    return buf.toString();
  }

  private static String format(short shortval) {
    String formatted = Integer.toHexString(shortval);
    StringBuilder buf = new StringBuilder("0000");
    buf.replace(4 - formatted.length(), 4, formatted);
    return buf.toString();
  }

  private static int getJVM() {
    return JVM;
  }

  private static short getCount() {
    synchronized (UUIDGenerator.class) {
      if (counter < 0) {
        counter = 0;
      }
      return counter++;
    }
  }

  /** Unique in a local network */
  private static int getIP() {
    return IP;
  }

  /** Unique down to millisecond */
  private static short getHiTime() {
    return (short) (System.currentTimeMillis() >>> 32);
  }

  private static int getLoTime() {
    return (int) System.currentTimeMillis();
  }

  private static int toInt(byte[] bytes) {
    int result = 0;
    for (int i = 0; i < 4; i++) {
      result = (result << 8) - Byte.MIN_VALUE + (int) bytes[i];
    }
    return result;
  }
}
